1. Technical Field
The following embodiments relate generally to a method and apparatus for providing FTN communication, and more particularly to a method and apparatus for providing FTN communication using transmit diversity.
2. Description of the Related Art
In a Nyquist transmission method used in conventional broadcast systems and communication systems, the shape of pulses and transmission speed are determined so as to enable signals to be transmitted without Inter-Symbol Interference (ISI) in a given bandwidth.
As a method for improving the transmission rate in a system using the Nyquist transmission method, there are a method of decreasing a pulse-shaping period, a method of raising a symbol modulation level, and the like.
However, decreasing a pulse-shaping period increases system bandwidth, and raising the symbol modulation level requires a higher Signal-to-Noise Ratio (SNR) for the same level of signal detection.
In order to overcome the limitations of existing transmission methods such as the Nyquist transmission method, a Faster-Than-Nyquist (FTN) transmission method, in which the transmission rate may be improved without using a higher modulation level in a given bandwidth, has been proposed.
The FTN transmission method is configured such that signals are transmitted with a shorter pulse-shaping period while maintaining a pulse shape, which is determined depending on bandwidth.
When signals are transmitted using the FTN transmission method, Inter-Symbol Interference (ISI) is necessarily generated in the transmitted signals. Here, ISI generated due to the FTN transmission method is called “FTN interference”.
Such FTN interference deteriorates signal detection performance. Here, if the pattern of the FTN interference is known in advance, a receiver may reconstruct original signals using various interference cancellation methods.
As a method for eliminating FTN interference, a method in which interference cancellation and channel decoding are repeatedly performed through interworking of an interference cancellation unit and a channel-decoding unit may be considered. This method has a structure in which the elimination of interference from a received signal sequence improves the performance of channel code and a channel-decoded sequence is used to further eliminate interference, whereby performance is gradually improved. Here, in order to use the channel-decoded sequence for interference cancellation, a method in which the prior probability of a received symbol sequence is applied depending on the configuration of an interference cancellation unit, a method in which FTN interference is estimated from a decoded signal sequence and is then eliminated, and the like may be considered.